New data on the molecular compounds of stereoisomeric ditertiary glycols of the series 1,4-di-(α-hydroxy-sec-alkyl)-cyclohexanes

Summary 1¹,4¹-Dihydroxy-1¹,4¹-diethyl-1,4-dipropylcyclohexanes, like the previously described 1¹,4¹-dihydroxy-1¹,4¹-dimethyl-1,4-diethylcyclohexanes, give a molecular compound of three molecules of cis- and one molecule of trans-form.     

Über die Cyclisierung von Histidinderivaten

Cyclisierung vonl-Histidin-methylester und Histamin über die (nicht isolierten) N-Phenylthiocarbonyl-derivate (Ia) führt durch intramolekulare Harnstoffbildung zu Derivaten des neuartigen bicyclischen Ringsystems Imidazo(1,5-c)tetrahydrooxopyrimidin (II, III).Dieses ist relativ beständig gegen saure Hydrolyse; Einwirkung von basischen Reagenzien (Alkali und Amine) und von Lithiumaluminiumhydrid führt unter Öffnung des Pyrimidinringes (zwischen 4 und 5) zur Bildung von 4(5)-substituierten Imidazolderivaten, wobei mit Aminen N-Carbonsäure-amide (V bis IX) und mit LAH in der Seitenkette N-methylierte Produkte (X, XI) entstehen.Untersuchungen an offenkettigen Modellsubstanzen mit ähnlicher Struktur (XVI, XVII) führten zu ähnlichen Ergebnissen — Abspaltung von Imidazol und entsprechender Substitution der zweiten Komponente, die in manchen Fällen primär als Isocyanat abgespalten wird. Für diese Reaktionen wird ein möglicher Mechanismus diskutiert.DieR _F-Werte einiger Imidazolderivate wurden bestimmt.     

Flow injection-spectrophotometric determination of cresol compounds in water by reaction withp-aminophenol

A spectrophotometric method has been developed for the simultaneous determination ofo-cresol andm-cresol in water by reaction withp-aminophenol (PAP). Three different methodologies have been assayed; (i) batch analysis, after reaction in an alkaline medium in the presence of dissolved molecular oxygen as oxidizing agent, (ii) a stopped-flow procedure, carried out in the presence of KIO₄ and (iii) a flow injection method based on the same approach. The batch procedure requires 22 min for the full development of colour witho-cresol and 12 min form-cresol. In the stopped-flow mode, using KIO₄ and a reaction time of 12 min, better sensitivity can be obtained for both compounds and limits of detection of 10 g 1^–1 foro-cresol and 30 g 1^–1 form-cresol were found. The flow injection method has a lower sensitivity but permits more than 80 injections per hour. Based on the different maximum absorbance wavelengths obtained for the reaction products of PAP witho-cresol (614 nm) andm-cresol (632 nm), both compounds can be simultaneously determined in water samples and recoveries of 90 to 115% were found in spiked water samples of different types.     

Improvement of the HPLC analysis of anthocyanins in red wines by use of recently developed columns

Comparison of the separation performance of five newly developed pH-stable HPLC columns is described for the analysis of anthocyanins in red wines. Separation of twenty anthocyanins in a single run is described using the most appropriate method.     

Bestimmung des Oxydationszustandes in Vanadiumkomplexen mit Hilfe von V—K-Röntgenabsorptionsspektren

Determination of the Oxydation State in Vanadium Complexes using V—K-Absorption Spectra The compounds resulting from the reaction of oxovanadium(IV) sulfate with 8-quinolinols in air were characterized by magnetic moments and V—K-absorption spectra. 8-quinolinol and its Mannich derivates (“CMAB-oxine”, “CMAP-oxine”) form vanadium(V) complexes. The oxovanadium(IV) compound of 7-methyl-8-quinolinol initially formed is not very stable in solution and tends to oxydation. Only the oxovanadium(IV) complex of 2-methyl-8-quinolinol has a good stability corresponding to that of β-diketone compounds.     

Microwave-assisted synthesis of sulfide M2S3 (m = Bi, Sb) nanorods using an ionic liquid

Single-crystalline Bi(2)S(3) and Sb(2)S(3) nanorods have been successfully synthesized by the microwave-assisted ionic liquid method. The starting reagents were Bi(2)O(3) or Sb(2)O(3), HCl, Na(2)S(2)O(3), and ethylene glycol (EG) or ethanolamine, and the ionic liquid used was 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIM][BF(4)]). Our experiments showed that the ionic liquid played an important role in the morphology of M(2)S(3) (M = Bi, Sb). Single-crystalline Bi(2)S(3) nanorods could be prepared in the presence of [BMIM][BF(4)]. However, urchinlike Bi(2)S(3) structures consisting of nanorods were formed without using [BMIM][BF(4)]. Single-crystalline Sb(2)S(3) nanorods were obtained in the presence of [BMIM][BF(4)]. However, single-crystalline Sb(2)S(3) nanosheets could be prepared in the absence of [BMIM][BF(4)]. The products were characterized by X-ray powder diffraction (XRD), transmission electron microscopy (TEM), and electron diffraction (ED).     

Free radicals in electrochemical reduction of 3,5-dicarbethoxy-1,4-dihydropyridines with nitrophenyl groups in positions 2, 4, and 6

In the electrochemical reduction of 2,6-bis- and 2,4,6-tris(nitrophenyl) derivatives of 3,5-dicarbethoxy-1,4-dihydropyridine, in the first stage, one of the para-nitrophenyl groups in position 2 or 6 of the heterocycle is reduced. Free radicals have been obtained and identified, the primary species being ion radicals of the nitrophenyl type. The presence of the heterocycle in the molecule of the 1,4-dihydropyridine derivative stabilizes secondary free radicals of the nitrosophenyl type. In the process of electrochemical reduction, no evidence has been found of any intramolecular transfer of electrons or protons from the dihydropyridine part of the molecule to the nitrophenyl groups. Derivatives of 2,6-bis(p-nitrophenyl)-3,5-dicarbethoxy-1,4-dihydropyridine have been synthesized, and the oxidation and methylation of these derivatives have been studied.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 481–487, April, 1991.     

Fragmentation of the unsubstituted carbohydrate units of cardenolide monosides

In the mass spectra of unsubstituted monosides of cardenolide nature are observed the M⁺ peaks, and also, in each case, three characteristic processes of the fragmentation of the carbohydrate unit. The formation of the ions AglOCH=OH⁺ is the most universal property of these compounds. The stability of ions of the type under consideration depends on the nature and position of attachment of the sugar residue and on the number of polar groups in the aglycone. The laws of the fragmentation of the carbohydrate unit are extended to the spectra of glycosides of other classes.Deceased.Institute of the Chemistry of Plant Substances, Academy of Sciences of the Uzbek SSR, Tashkent. Translated from Khimiya Prirodynykh Soedinenii, No. 3, pp. 345–354, 1983.     

Successive substitution titration of calcium and magnesium with EGTA using thallium oxide electrode for indication

Summary It is demonstrated that magnesium can be titrated with EGTA in the presence of CaEDTA complex. On the basis of this substitution reaction, calcium and magnesium are successively titrated with EGTA, if an appropriate amount of CaEDTA is added after having reached the end point for calcium. Both end points are indicated amperometrically using a thallium oxide anode. The method has been tested for analysis of tap and mineral water. Larger amounts of manganese(II) render the calcium result too high. Moreover, the indication of both end points is affected by the electrode position of an inactive MnO₂-layer onto the Tl₂O₃-layer. Reducing agents destroy the Tl₂O₃-layer. These interferences can be overcome by addition of an appropriate amount of manganate(VII) to the sample.

---

Sukzessive Substitutionstitration von Calcium und Magnesium mit ÄGTA, indiziert mit der Thalliumoxidelektrode

Zusammenfassung Magnesium kann mit ÄGTA in Gegenwart des CaÄDTA-Komplexes titriert werden. Auf der Grundlage dieser Substitutionstitration können Calcium und Magnesium nacheinander mit ÄGTA titriert werden, wenn nach dem Endpunkt für Calcium eine ausreichende Menge CaÄDTA zugesetzt wird. Beide Endpunkte werden amperometrisch mit Hilfe einer Thalliumoxidelektrode angezeigt. Die Methode wurde an Leitungswasser und Mineralwasser geprüft. Größere Mengen Mangan(II) bewirken zu hohe Calciumwerte. Darüber hinaus wird die Indikation beider Endpunkte dadurch beeinträchtigt, daß sich eine inaktive MnO₂-Schicht auf der Tl₂O₃-Schicht elektrolytisch abscheidet. Reduzierende Stoffe zerstören die Tl₂O₃-Schicht. Diese Störungen können durch Zugabe von Permanganat vermieden werden.

     

Infrared and Raman spectral interpretations of the ferroelectric phases of NaH3(SeO3)2 and NaD3(SeO3)2

The infrared and Raman spectra of NaH₃(SeO₃)₂ and NaD₃(SeO₃)₂ have been recorded from 24 to 300°K. The interpretation, assignments, and analysis of the spectral studies are presented on the paraelectric α phase (proton disordered), ferroelectric β phase (proton ordered) and ferroelectric γ phase (proton ordered). A discussion of a newly proposed proton-triggered phase transition mechanism and a possible origin of the hydrogen-bonded OH stretching region of KH₂PO₄-type ferroelectrics is given.